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Duplication multiplexing????

Created: 23 Jun 2012 | 6 comments

Any idea when duplication multiplexing will be available? When I look at my drives as a duplication is happening...it is shoe-shining. Write a little data....spin the tape...write a little data....spin the tape. The manufacturer of the drives says this is a BIG problem with Netbackup an duplication jobs. I have replaced 3 L5 drives in the past month. I can olny assume it is due to the duplication jobs. Thank god for waranties.

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Marianne's picture

Please share more info:

NBU version as a start, as things are done differently across various NBU versions.
OS on media servers and resource capabilities to efficiently drive LTO5?

Type of duplication - SLP? DSSU? Vault?
Documentaion available for each type explaining how images are grouped into 'chunks' for efficient duplication.

Information on source and destination STU?
Basic Disk to Tape? VTL to tape? Advanced or OST to Tape?
Local SAN duplication on same media server or across network from one media server to another?
If local disk to tape, are tapes and disk zoned to different HBA's?

We see excellent duplication rates with local duplications - maintained rate of more that 100 Mb/sec using LTO3.

As you can see, there are LOTS of factors that play a part in data transfer. It is therefore extremely irresponsible of your tape vendor to make blanket statements.

OK, I see in one of many tags that you seem to be on NBU 7.5.

Supporting Storage Foundation and VCS on Unix and Windows as well as NetBackup on Unix and Windows
Handy NBU Links

mph999's picture

If using SLP, there is an option to 'preserve multiplexing' - so I would sugest this is already available.

From page 552 of 7.5 Unix Admin Guide 1

Select whether to Preserve multiplexing. This option is available for
Duplication operations that use tape media or virtual tape libraries (VTL).
 
As Marianne asked, what type of duplication are you using.
 
Martin
Regards,  Martin
 
Setting Logs in NetBackup:
http://www.symantec.com/docs/TECH75805
 
Bmitche's picture

I am backing up to a media server dedupe pool(puredisk) on windows2008 R2. The storage is direct attached(6gb sas). The LTO5 drives aew direct attached to same media server via 8gb fiber. My issue is not with the disk or tape speed. It is with duplication using a simple SLP. The duplication jobs are "single" threaded. Even if I check preserve multiplexing...it's still single threaded. Here is an example...If I backup 15 servers(100gb of data) stright to a tape and use multiplexing....the job will finish in approx. 1hr. If I use an SLP to goto the media server dedupe pool, then duplicate to tape....the duplication may take approx. 2hrs.

Marianne's picture

Are you aware of the SLP best practise guide? http://www.symantec.com/docs/TECH66149

It describes how backup images can be grouped in bigger 'chunks'.

Rehydration has been a 'known issue' when duplicating from MSDP to tape: http://www.symantec.com/docs/TECH161039

Not sure if the 'fixes' mentioned in this TN has made it into 7.5 binaries. You may want to have a look at 7.5.0.1 and 7.5.0.3 Release Notes. Look for improvements related to rehydration.

Problem also discussed in this thread: https://www-secure.symantec.com/connect/forums/net...

Supporting Storage Foundation and VCS on Unix and Windows as well as NetBackup on Unix and Windows
Handy NBU Links

thesanman's picture

As per best practice my SLP rehydrate to disk first; then push the images off to tape.  Stops any issues.

NBU v7.5.0.6 Master and Media servers on RHEL 5/6 & Win2008; SAN based LTO3, 4 and 6 tape libraries
Linux, Solaris, Windows and OpenVMS clients.
PureDisk, SLP, VMware, HyperV, Oracle, Netezza, SQL/Server,

Marianne's picture

No, MSDP dedupes when writing to disk. Data is rehydrated (opposite of dedupe) when copied to tape.
The process of finding all the bits and pieces to send to tape in non-dedupe format (rehydrate) is what is taking so long.

Supporting Storage Foundation and VCS on Unix and Windows as well as NetBackup on Unix and Windows
Handy NBU Links